[7] Westerlund 1 W237 is classified as a luminous cool supergiant emitting most of its energy in the infrared spectrum.

The initial mass of W237 has been calculated from its position relative to theoretical stellar evolutionary tracks to be around 28 M☉ or 32 M☉ for a non-rotating star.

[9] The distance of Westerlund 1 W237 is assumed to be around 8,500+2,000−1,300 light years or 2,600+600−400 parsecs[12] based on it being commonly thought of as a member of the Westerlund 1 star cluster (the elliptical shape of its nebula indicates that it might not be near the center of W1, while other RSGs like W20 and W26 are).

[7] Westerlund's 1987 analysis assigned a spectral type of M6+ III to W1-237 and considered it to be a foreground giant with a luminosity only around 1,000 L☉.

[2] Gaia Data Release 2 gives a parallax of 1.64±0.2608 mas for W237, implying a distance of 623+139−96 pc and a luminosity of 7,178–7,379 L☉ with a corresponding radius of 216 R☉.